"Without aid it is so. But suppose you had a friend up here who
lowered you this good stout rope which I see in the corner,
securing one end of it to this great hook in the wall. Then, I
think, if you were an active man, You might swarm up, wooden leg
and all. You would depart, of course, in the same fashion, and
your ally would draw up the rope, untie it from the hook, shut
the window, snib it on the inside, and get away in the way that
he originally came. As a minor point it may be noted," he
continued, fingering the rope, "that our wooden-legged friend,
though a fair climber, was not a professional sailor. His hands
were far from horny. My lens discloses more than one blood-mark,
especially towards the end of the rope, from which I gather that
he slipped down with such velocity that he took the skin off his
hand."

"This is all very well," said I, "but the thing becomes more
unintelligible than ever. How about this mysterious ally? How
came he into the room?"

"Yes, the ally!" repeated Holmes, pensively. "There are features
of interest about this ally. He lifts the case from the regions
of the commonplace. I fancy that this ally breaks fresh ground
in the annals of crime in this country,--though parallel cases
suggest themselves from India, and, if my memory serves me, from
Senegambia."

"How came he, then?" I reiterated. "The door is locked, the
window is inaccessible. Was it through the chimney?"

"The grate is much too small," he answered. "I had already
considered that possibility."

"How then?" I persisted.

"You will not apply my precept," he said, shaking his head. "How
often have I said to you that when you have eliminated the
impossible whatever remains, HOWEVER IMPROBABLE, must be the
truth? We know that he did not come through the door, the
window, or the chimney. We also know that he could not have been
concealed in the room, as there is no concealment possible.
Whence, then, did he come?"

"He came through the hole in the roof," I cried.

"Of course he did. He must have done so. If you will have the
kindness to hold the lamp for me, we shall now extend our
researches to the room above,--the secret room in which the
treasure was found."

He mounted the steps, and, seizing a rafter with either hand, he
swung himself up into the garret. Then, lying on his face, he
reached down for the lamp and held it while I followed him.

The chamber in which we found ourselves was about ten feet one
way and six the other. The floor was formed by the rafters, with
thin lath-and-plaster between, so that in walking one had to step
from beam to beam. The roof ran up to an apex, and was evidently
the inner shell of the true roof of the house. There was no
furniture of any sort, and the accumulated dust of years lay
thick upon the floor.

"Here you are, you see," said Sherlock Holmes, putting his hand
against the sloping wall. "This is a trap-door which leads out
on to the roof. I can press it back, and here is the roof
itself, sloping at a gentle angle. This, then, is the way by
which Number One entered. Let us see if we can find any other
traces of his individuality."

He held down the lamp to the floor, and as he did so I saw for
the second time that night a startled, surprised look come over
his face. For myself, as I followed his gaze my skin was cold
under my clothes. The floor was covered thickly with the prints
of a naked foot,--clear, well defined, perfectly formed, but
scarce half the size of those of an ordinary man.

"Holmes," I said, in a whisper, "a child has done the horrid
thing."

He had recovered his self-possession in an instant. "I was
staggered for the moment," he said, "but the thing is quite
natural. My memory failed me, or I should have been able to
foretell it. There is nothing more to be learned here. Let us
go down."

"What is your theory, then, as to those footmarks?" I asked,
eagerly, when we had regained the lower room once more.

"My dear Watson, try a little analysis yourself," said he, with a
touch of impatience.